Technical Field
The present invention relates to coding using High Efficiency Video Coding (HEVC or H-265). More particularly, the present system relates to motion vector prediction for coding of HEVC blocks.
Related Art
State of the art video quality is achieved today by performing complex High Efficiency Video Coding (HEVC) video encoding with the video pictures broken into macroblocks. Motion vector determination enables more efficient coding of the blocks making up a picture. The HEVC coding standard (also called H.265) is a coding standard promulgated by the ISO/IEC MPEG standardization organizations. HEVC supports resolutions higher than “high definition,” which means pixels may be represented by a larger number of bits than the high definition pictures. For example, 4K resolutions may include images that are 4,000 pixels wide compared to high definition images that are 1920 pixels wide.
Temporal motion prediction is an effective method to increase the coding efficiency and provides high compression necessary for HEVC. HEVC uses a translational model for temporal motion prediction. According to the translational model, a prediction signal for a given current unit in a current picture is generated from a corresponding reference unit in a reference picture. The coordinates of the reference unit are given by a motion vector that describes the translational motion along horizontal (x) and vertical (y) directions that would be added/subtracted to/from the coordinates of the current unit. A decoder needs the motion vector to decode the compressed video.
HEVC relies on a block based translational model for its temporal prediction (inter coding) in order to keep complexity and overhead bits low. For inter coding block, HEVC designates a prediction block as an area for motion compensation where all the pixels inside the prediction block performs identical translation temporally using either one or two motion vectors (MV). Motion vector prediction is used to code motion vector(s) to reduce the overhead bits for motion vector signaling. Motion estimation or prediction is a process of determining a motion vector (MV) for a current unit of video. The motion estimation process searches for a best match prediction for a current unit block of video (e.g., a prediction block) over reference pictures. For a current inter block, its motion vector predictor can be derived from the motion vectors of its spatially neighboring blocks and/or the temporally collocated block.
It is desirable to provide improvements in motion vector prediction accuracy to make HEVC coding more efficient.